Bending machine

ABSTRACT

A bending machine includes a frame, a punch holder provided on the frame, a die holder provided on the frame, a pressing mechanism for pressing a punch toward a die, a first deflection detector for detecting a stroke of the punch, a second deflection detector for detecting an actual displacement of the punch, and a controller; and the controller previously stores a relation between a deflection of the frame and a specification of a sheet material, calculates an actual deflection of the frame by subtracting a detection value of the second deflection detector from a detection value of the first deflection detector, gets a target deflection of the frame based on the relation stored, and controls the pressing mechanism so that the actual deflection becomes consistent with the target deflection. According to the bending machine, working efficiency can be improved by rendering a trial bending unnecessary.

TECHNICAL FIELD

The present invention relates to a bending machine for bending sheetmaterials, especially, relates to a bending machine that requires notrial bending.

BACKGROUND ART

A Patent Document 1 listed below discloses a prior-art bending machine(press brake). In the bending machine, a punch-side table provided witha punch is disposed on its one side (upper side), and a die-side tableprovided with a die is disposed on its other side (lower side). A sheetmaterial is bent between the punch and the die by stroking the punch toapply pressure to sheet material. A stroke of the punch is detected by apunch detector. The stroke may be changed by a thermal deformation of aframe. Therefore, when the stroke detected by the punch detector is notan expected amount, bending is done accurately by compensating thestroke.

In the above bending machine, a trial bending(s) is done for eachspecification [material, sheet thickness, shape (bending length)] ofsheet materials to be bent. By setting a pressing force or a strokeaccording to the trial bending and then bending with the pressing forceor the stroke that has been set, a bending work(s) can be automated.

As such a bending work, there are two types of working methods, airbending and coining. Note that air bending can be further classifiedinto partial bending and bottoming. Namely, a bending work can beclassified into three types working methods, partial bending, bottomingand coining.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2000-343128

SUMMARY OF INVENTION

Since air bending requires a small pressing force but brings a widedispersion of a bent angle, its bending accuracy is not high. In orderto improve accuracy of a bent angle by air bending with no trial bendingfor each specification of sheet materials to be bent, an angle sensor(s)is required. However, an automated bending machine is equipped with anautomated tool changer, so that it is difficult to use an anglesensor(s). Therefore, it is required, for air bending, to set anadequate pressing force or an adequate stroke of a punch through a trialbending(s) for each specification of sheet materials to be bent. Coiningis done with a ten to twelve times larger pressing force than a pressingforce for air bending and thereby brings high accuracy, but it isproblematic in that its pressing force becomes too large relative to abending length.

As explained above, for the prior-art bending machine, a trialbending(s) is required for each specification of sheet materials to bebent to set an adequate pressing force or an adequate stroke (a goodworking condition), and thereby there are problems in view of workingefficiency.

Therefore, an object of the present invention is to provide a bendingmachine that can improve working efficiency by rendering a trial bendingunnecessary and can bring a good working condition.

An aspect of the present invention provides a bending machine thatincludes a frame that includes a base section, and a punch-side framesection and a die-side frame section that are extended from both sidesof the base section in an identical direction, respectively, a punchholder that is provided on the punch-side frame section and to which apunch is attached, a die holder that is provided on the die-side framesection and to which a die is attached, a pressing mechanism thatpresses the punch toward the die to bend a sheet material between thedie and the punch, a first deflection detector that is provided in thepressing mechanism and detects a displacement of the punch required forbending the sheet material, a second deflection detector that issupported by the die-side frame section and detects an actualdisplacement of the punch, and a controller operable to previously storea relation between a deflection of the frame 2 and a bending length,material and a sheet thickness of a sheet material, to calculate anactual deflection of the frame by subtracting a detection value of thesecond deflection detector from a detection value of the firstdeflection detector, to get a target deflection of the frame for bendinga sheet material to be bent based on the relation stored, and to controlthe pressing mechanism so that the actual deflection becomes consistentwith the target deflection.

According to the above aspect, the controller stores the relationbetween a deflection of the frame and a bending length, material and asheet thickness of a sheet material, and the pressing mechanism iscontrolled so that the actual deflection of the frame that is calculatedbased on the detection values of the first deflection detector and thesecond deflection detector is made consistent with the target deflectionassociated with a sheet material to be bent (and retrieved based on therelation). Therefore, the sheet material can be bent under a goodworking condition, and, further, no trial bending is required. As aresult, working labors for bending a sheet material can be reduced.

Here, it is preferable that the pressing mechanism includes a motor forpressing that moves the punch toward the die, the first deflectiondetector is an encoder that detects rotations of the motor, and thesecond deflection detector is a scale that is supported by the die-sideframe section via a support frame.

According to this, since the first deflection detector is the encoder ofthe motor for moving the punch and the second deflection detector is thescale for detecting the displacement of the punch, the actual deflectionof the frame can be directly detected while bending a sheet material.Therefore, the controller can be control the motor precisely.

In addition, it is preferable that the controller includes a deflectioncalculator that calculates the actual deflection of the frame fromdetection results of the first deflection detector and the seconddeflection detector, and a memory for storing a data table in which therelation is defined.

According to this, since the deflection calculator calculates the actualdeflection of the frame and the data table in which the above relationis defined is stored in the memory, the relation between a deflectionand a sheet material can be perceived accurately. Therefore, a sheetmaterial can be bent successfully with no trial bending.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 It is an overall front view of a bending machine according to anembodiment.

FIG. 2 It is a block diagram of a controller in the bending machine.

FIG. 3 It is a flowchart for a drive control for the bending machine.

FIG. 4 It shows tables stored in the controller.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a bending machine according to an embodiment will beexplained. The bending machine 1 includes a frame 2, a pressingmechanism 3, a detection mechanism 4, and a controller 5.

The frame 2 is configured of a base section 21 having a given length,and a punch-side frame section 23 and a die-side frame section 25 thatare integrally extended from both sides of the base section 21,respectively. The punch-side frame section 23 and the die-side framesection 25 are vertically extended from the base section 21 in anidentical direction, respectively. A punch 6 and the pressing mechanism3 are provided on the punch-side frame section 23. A die 7 is providedon the die-side frame section 25.

The pressing mechanism 3 includes a ball screw 30 supported on thepunch-side frame section 23, and a motor 32 for pressing. The ball screw30 can move linearly along its axial direction. A coupling bracket 31 iscoupled to an end of the ball screw 30. A punch holder 8 is attached tothe coupling bracket 31. The punch 6 is attached to an end of the punchholder 8. The punch 6 presses a sheet material due to a movement of theball screw 30, and thereby the sheet material is bent between the punch6 and the die 7. The punch 6 is moved by the motor 32.

The motor 32 has a reduction gear 33 on its output side. A nut 34 iscoupled with the reduction gear 33. The ball screw 30 is meshed with thenut 34 to penetrate therethrough. When the nut 34 is rotated in itsforward/backward direction by the motor 32, the ball screw 30 moveslinearly in its feeding/reversing direction. Then, a sheet material ispressed due to the movement of the ball screw 30 in the feedingdirection, and thereby the sheet material is bent. In this case, it isrequired to restrict a rotation of a screw of the ball screw 30 so thatthe screw is not passively rotated along with the rotation of the nut34. Therefore, an anti-rotation unit 38 is provided in the pressingmechanism 3.

The rotation of the motor 32 is controlled by the controller 5. Inaddition, the number of rotations of the motor 32 is detected by anencoder 11. The encoder 11 is a first deflection detector, and an actualstroke of the punch 6 toward the die 7 is detected by detecting thenumber of rotations of the motor 32. Note that the stroke detected bythe encoder 11 includes a deflection of the frame 2 caused by pressing asheet material. A detection result of the encoder 11 is output to thecontroller 5.

Further, a motor 36 for high-speed feeding is provided in the pressingmechanism 3. The motor 36 moves the punch 6 at high speed to a positionjust before nipping a sheet material. The motor 36 is coupled to thecoupling bracket 31 via a reduction gear 35.

The die 7 is attached to a die holder 10. The die holder 10 is attachedto the die-side frame section 25 of the frame 2. The die holder 10 isattached to the die-side frame section 25 so that the die 7 and thepunch 6 face to each other. The detection mechanism 4 is disposed nearthe die holder 10 on the frame 2.

The detection mechanism 4 includes a support frame 41 supported by thedie-side frame section 25, and a scale 42 attached to the support frame41. The detection mechanism 4 is configured so that, even when areactive force is generated against a pressing force for bending a sheetmaterial, the reactive force doesn't act on the support frame 41. Thescale 42 is disposed near the punch holder 8, and detects a relativeposition of the punch holder 8 to the die holder 10. The scale 42 is notdirectly fixed with the frame 2, but attached to the frame 2 via thesupport flame 41. Since the reactive force doesn't act on the supportframe 41, the scale 42 can detect an actual displacement of the punch 6without a deflection of the frame 2. Namely, the scale 42 is a seconddeflection detector that detects an actual displacement of the punch 6when pressing a sheet material. A detection result of the scale 42 isoutput to the controller 5.

The controller 5 includes a deflection calculator 51, and data tables53. The controller 5 controls the motor 32 and the motor 36. Thedeflection calculator 51 calculates a deflection of the frame 2 whenpressing a sheet material. The deflection of the frame 2 can becalculated by subtracting a detection value of the scale 42 (the seconddeflection detector) from a detection value of the encoder 11 (the firstdeflection detector). Specifically, the deflection of the frame 2 can beobtained by (detection value of the encoder 11)−(detection value of thescale 42).

The data tables 53 are stored in a memory 56 (explained later) in thecontroller 5. In the data tables 53, recorded are relations between acalculated deflection of the frame 2 and a bending length, material anda sheet thickness of a sheet material. The controller 5 determines adeflection of the frame 2 associated with a bending length, material anda sheet thickness of a sheet material, and then controls the motor 32 soas to achieve the deflection.

FIG. 2 is a block diagram showing the controller 5. In the controller 5,an input interface 54, an output interface 55 and the memory 56 areconnected with a CPU 58 by a data bus 57. It can be said that theabove-explained deflection calculator 51 is configured of thesecomponents. In addition, the encoder 11, the scale 42, the motor 32 andthe motor 36 that are explained above are also connected with the databus 57.

The input interface 54 inputs various data to the CPU 58, and, forexample, a keyboard and an external disk drive are connected to theinput interface 54. The output interface 55 outputs data from CPU 58,and, for example, a display and a printer are connected with the outputinterface 55. Data and a work program that are input from the inputinterface 54 and the above-explained data tables 53 are stored in thememory 56. In addition, the detection results of the encoder 11 and thescale 42 are controlled by commands output from the CPU 58 via the databus 57.

Next, a pressing control for bending by bottoming based on a deflectionof the frame 2 will be explained.

First, a relation between a deflection δ of the frame 2 and a pressingforce F is measured by a load sensor such as a load cell. Structurallooseness and deformation become evident as the deflection δ of theframe 2 while the pressing force F is small, so that the relationbetween the deflection δ of the frame 2 and the pressing force F can bedescribed by an exponential function δ=a×F^(b) (a, b are constants). onthe other hand, while the pressing force F is large, the relationbetween the deflection δ of the frame 2 and the pressing force F can bedescribed by a linear function δ=c×F+d (c, d are constants). Namely, therelation between the deflection δ and the pressing force F can bedescribed by δ=a×F^(b) [while F is small] or c×F+d [while F is large] .. . (I). Alternatively, the relation between the deflection δ and thepressing force F can be also described by F=(δ/a)^(1/b) [while F issmall] or (δ−d)/c [while F is large] . . . (II).

A pressing force required for bottoming is determined thorough workingtests separately from actual bendings. The working tests are done wheninitially setting the bending machine 1, and are not a trial bending(s)done for each specification of sheet materials. FIG. 4 shows the datatables 53 each of which indicates a relation between a sheet material[sheet thickness·material] and a deflection of the frame. In the workingtests, a bending length (L1=0.5, L2=1.0, L3=2.0, . . . [unit: m]) isprepared for each sheet materials (A, B, . . . ) [specification: sheetthickness (t1, t2, . . . )·material (m1, m2, . . . )], and deflection(s)δ of the frame 2 that makes a bent angle after bending to 90°±15° ismeasured. In the present embodiment, as shown in FIG. 4, the data tables53 are made for every sheet material, and the deflection δ is stored inthe data tables 53 for each of the above sheet materials. Note that itmay be possible to make one data sheet 53 by regarding types of sheetmaterials as a parameter.

The measured deflections δ of the frame 2 are converted to the pressingforces F by the above equation (II), respectively. For example, withrespect to a sheet material A, F_(AL1), F_(AL2), . . . are calculated(similarly to a sheet material B). Further, the pressing forces Fconverted are further converted to converted pressing forces F′=F/L perunit length L [1 m]. For example, with respect to the sheet material A,F′_(AL1), F′_(AL2), . . . are calculated (similarly to a sheet materialB). Then, calculated is an average value Z of all the pressing forces F′per unit length with respect to each bending length L (L1, L2, L3 . . .) for each of the sheet materials (A, B, . . . ). For example, withrespect to the sheet material A [(t1, m1)], calculated is an averageZ_(A) of F′_(AL1), F′_(AL2), . . . F′_(ALn) (similarly to a sheetmaterial B). These average values are stored, in the controller 5, forevery sheet materials (A, B, . . . ) as the required pressing force Z(Z_(A), Z_(B), . . . ) per unit length.

Next, a control of bending (bottoming) by use of the above-explaineddata tables 53 will be explained with reference to a flowchart shown inFIG. 3.

First, data of a sheet material to be bent are input to the controller 5(step S11). The data of the sheet material are a bending length, a sheetthickness and its material. The controller 5 calculates a targetpressing force Ft required for bottoming based on an equation F=Ld×Z.Here, Ld is the bending length in the data input in step S11. Z is therequired pressing force for the sheet material [sheetthickness·material] of the data input in step S11, and is stored in thecontroller 5 through the above-explained working tests.

Subsequently, a target deflection δt of the frame 2 is calculated by theabove equation (I) based on the calculated target pressing force Ft(step S12). In other words, the target deflection δt of the frame 2 isdetermined based on the target pressing force Ft calculated in step S11.Namely, when the frame 2 involves the deflection δt, it can be regardedthat the target pressing force Ft is applied to the sheet material.

The controller 5 does pressing by driving the motor for pressing (stepS13). At this time, the detection results of the encoder 11 and thescale 42 are output to the controller 5. The deflection of the frame 2due to pressing is measured (step S14). The motor 32 is controlled withfeedback based on the value calculated by subtracting the detectionvalue of the scale 42 from the detection value of the encoder 11, i.e.the actual deflection δ. Specifically, the motor 32 is controlled withfeedback so that the actual deflection δ of the frame 2 is madeconsistent with the target deflection δt.

When the deflection δ measured in step S14 becomes consistent with thetarget deflection δt determined in step S12, i.e. when the actualpressing force F becomes consistent with the target pressing force Ft,the controller 5 stops the motor 32 (step S15), and bending of the sheetmaterial is finished. If the deflection δ measured in step S14 doesn'tbecome consistent with the target deflection δt determined in step S12,the process flow returns to step S13 and driving of the motor 32 iscontinued by the controller 5.

In the present embodiment, the controller 5 stores data of relationsbetween a deflection of the frame 2 and a bending length, material and asheet thickness of a sheet material, and calculates, based on the storeddata, a target deflection of the frame 2 associated with a bendinglength, material and a sheet thickness of a sheet material, and thencontrols the motor 32 so that an actual deflection of the frame 2becomes consistent with the target deflection. Therefore, a sheetmaterial can be bent under a good working condition, so that a trialbending(s) can be rendered unnecessary and working labors for bending asheet material can be reduced.

In addition, since the deflection of the frame 2 is detected by theencoder 11 of the motor 32 for pressing and the scale 42 for detectingthe displacement of the punch 6 in the present embodiment, thedeflection of the frame 2 can be directly detected while bending a sheetmaterial. Therefore, the controller 5 can control the motor 32precisely.

Further, since the controller 5 includes the deflection calculator 51and the data tables 53 that indicate relations between a deflection anda bending length, material and sheet thickness of a sheet material, arelation between deflection of the frame 2 and a sheet material can beperceived accurately and thereby a sheet material can be bentsuccessfully with no trial bending.

1. A bending machine comprising: a frame that includes a base section,and a punch-side frame section and a die-side frame section that areextended from both sides of the base section in an identical direction,respectively; a punch holder that is provided on the punch-side framesection and to which a punch is attached; a die holder that is providedon the die-side frame section and to which a die is attached; a pressingmechanism that presses the punch toward the die to bend a sheet materialbetween the die and the punch; a first deflection detector that isprovided in the pressing mechanism and detects a stroke of the punchrequired for bending the sheet material; a second deflection detectorthat is supported by the die-side frame section and detects an actualdisplacement of the punch; and a controller operable to previously storea relation between a deflection of the frame and a bending length,material and a sheet thickness of a sheet material, to calculate anactual deflection of the frame by subtracting a detection value of thesecond deflection detector from a detection value of the firstdeflection detector, to get a target deflection of the frame for bendinga sheet material to be bent based on the relation stored, and to controlthe pressing mechanism so that the actual deflection becomes consistentwith the target deflection.
 2. The bending machine according to claim 1,wherein the pressing mechanism includes a motor for pressing that movesthe punch toward the die, the first deflection detector is an encoderthat detects rotations of the motor, and the second deflection detectoris a scale that is supported by the die-side frame section via a supportframe.
 3. The bending machine according to claim 1, wherein thecontroller includes a deflection calculator that calculates the actualdeflection of the frame from detection results of the first deflectiondetector and the second deflection detector, and a memory for storing adata table in which the relation is defined.